How to change color of the currently active window in Blender?
You can edit your theme using Edit &gt; Preferences &gt; Themes.  From there, go to each panel, then open the Theme space dropdown, and set the Header colour:

You'll have to do this for each menu, I don't think there's a setting for all the menus.
Theme docs: https://docs.blender.org/manual/en/latest/editors/preferences/themes.html